1. Field of the Invention
The present invention relates in general to acoustic emission leak detection systems, and, in particular, to an acoustic emission (AE) leak simulator for calibrating and/or characterizing current acoustic emission leak detection systems for verification of their integrity.
2. Description of the Related Art
In recent years, an increasing amount of interest has been shown by utilities in the capability for early leak detection in high pressure components, such as boiler waterwalls, steam lines or high pressure feedwater heaters. Consequently, utilities have purchased and installed acoustic leak detection systems. Presently, there are two basic routes to detect leakage in various pressure components. In the furnace and convection pass areas of boilers, audible airborne (20 Hz-20 kHz) noise level tracking has shown great success. For steam lines, feedwater heaters, and cyclone boilers, high frequency structure-borne (50 kHz-1 MHz) noise level tracking is more prominent.
For the airborne leak detection systems, troubleshooting of the installations as well as periodic calibrations are enabled by artificial airborne leak sound wave generators.
However, there currently is no structure-borne analog for the air-borne leak simulator. Thus, it is not possible to directly prove that structure-borne systems are operating properly and detect a leak of a certain size at a given distance prior to an actual leak incident. In addition, it is quite difficult to develop new applications since sensor spacing essentially remains guess work.
An article titled "Advances in Acoustic Leak Monitoring Instrumentation", IEEE Trans. on Nucl. Sci., Vol. NS-30, No. 1, pp. 825-832, February, 1983, describes a method of testing a system or simulation. It discusses an air jet testing procedure where a small nozzle directs air or some other gas at the pipe's surface to generate a wide band, random noise acoustic signal. The root means square (RMS) voltage output of the sensor under test is then recorded as the measure of absolute sensitivity.
Accordingly, there is a need for an acoustic emission leak simulator which adequately characterizes current structure-borne leak detection systems to verify their integrity. It should also provide sensor spacings in new applications.